House Screening - Biological and Environmental Control of Disease Vectors - page 126

(a) (b)

(c)

Fig. 7.2. (a) Door, (b) ceiling and (c) eaves screened with PVC-coated fi breglass netting (author's own
photographs).

lymphatic fi lariasis (LF), Rift Valley fever and
West Nile virus in parts of West Africa (Diallo et
al ., 2005) and LF in Asia (White, 1989).
Data on eave entry by other culicine species
are much less clear and sometimes contra-
dictory (Kohn, 1991; Charlwood et al ., 2003;
Howell and Chadee, 2007; Njie et al ., 2009;
Ogoma et al ., 2010). Where only eaves are
screened, Culex quinquefasciatus , Cx . univittatus
and Cx . theileri numbers indoors may be
unaf ected or even increase (Ogoma et al ., 2010).
Several Stegomyia species are low fl ying and
most frequently encountered at <1 m from the
ground. Many are also day-biting species that
are less likely to encounter humans indoors.
Data on eave entry by other vectors are scarce.
Because of the association with roofi ng
materials (e.g. Cohen et al ., 2006) triatomine
bugs may enter houses predominantly through
eaves or directly from the roof in the absence of

a ceiling. Anecdotal evidence suggests that,
following house improvement (including repairs
in which eaves were blocked and construction of
new houses without eave gaps), triatomine bugs
do not return to houses (Briceno-Leon, 1987).

7.4.2 Ceilings

Much of what has been said about eaves also
applies to ceilings. If present at all in tropical
rural houses, ceilings are typically horizontal
surfaces of wood, cardboard, palm leaves, cloth
or sacking, supported by the walls and installed
below the eave space, thus forming the upper
interior limit of a room. Ceilings prevent
mosquitoes that have entered through the eaves
from accessing hosts in the room space, trapping
them in the roof space unless they exit again
through the eaves.